In a tandem type full-color image forming apparatus in the related art, there has been proposed a technique for preventing misregistration such as misregistration in a conveyance direction of an intermediate transfer belt, misregistration in a scanning direction, a variation of an oblique inclination, a variation of a magnification error, etc. as follows. That is, a reflector is disposed in a light beam optical path from a scanning optics to a photoconductor drum so that the position of the reflector can be adjusted. The positions of marks on the intermediate transfer belt are detected. Misregistration factors among respective images are corrected in accordance with the detection result (Japanese Patent No. 2,603,254).
In Japanese Patent No. 2,603,254, marks of four colors are formed whenever misregistration factors among respective images are to be corrected. Accordingly, there is a problem that the consumption of color toners increases and it takes much processing time to correct misregistration.
Further, there has been proposed a tandem type full-color image forming apparatus in which four image forming cartridges can be removably attached to a body unit. In each image forming cartridge, a photoconductor drum, a cleaner, a charger, a developing unit, etc. are incorporated integrally and formed into a unit. When the image forming cartridges are inserted or removed for exchanging expendables, misregistration is apt to occur due to the exchange. In order to improve this point, there has been proposed an image forming apparatus arranged out of two kinds of image forming cartridges one of which is a monochrome image forming cartridge and the other of which is a three-color-integrated image forming cartridge (JP-A-9-304994)
When color misregistration among images of respective colors is to be corrected in an image forming apparatus as disclosed in JP-A-9-304994, registration is usually controlled with registration marks of four colors formed on an intermediate transfer belt. Accordingly, there is a problem that the consumption of color toners increases and it takes much processing time to correct color misregistration.
The present invention is aimed at solution to the foregoing problem. A first object of the invention is to provide an image forming apparatus capable of changing over between black printing and color printing, in which registration adjustment can be performed with suppressed toner consumption and shortened processing time.
In order to attain the first object, a first embodiment of the invention provides an image forming apparatus capable of changing over between black printing and color printing with an intermediate transfer belt being brought into contact with and separated from photoconductors by means of a black transfer member and a three-color-integrated color transfer member, the image forming apparatus including: a registration mark former for forming registration marks on the intermediate transfer belt; a registration sensor for reading the registration marks; and a controller for controlling the registration mark former based on the registration marks read by the registration sensor, so as to adjust registration; wherein the controller has an adjustment mode to adjust registration between black and color.
In addition, the controller may have a first adjustment mode in which a registration mark of one of yellow, magenta and cyan and a registration mark of black are formed individually so as to adjust registration between black and color, and a second adjustment mode in which registration marks of all the colors are formed to adjust registration, and the controller may change over between the first adjustment mode and the second adjustment mode so as to adjust registration.
Further, the controller may adjust registration using a registration mark of black and a registration mark of a color whose photoconductor is located in a position closest to a black photoconductor.
Further, the controller may change over the color whose registration marks should be formed, in accordance with remaining amounts of toners.
According to the first embodiment of the invention, the image forming apparatus having a black transfer member and a three-color-integrated color transfer member has an adjustment mode to adjust registration between black and color in which misregistration is apt to occur. Accordingly, the consumption of color toners can be suppressed, and the processing time for registration adjustment can be shortened.
In addition, registration adjustment is performed by changing over between the first adjustment mode in which a registration mark of one of yellow, magenta and cyan and a registration mark of black are formed individually so as to adjust registration between black and color, and the second adjustment mode in which registration marks of all the colors are formed to adjust registration. Accordingly, the consumption of color toners can be suppressed, and the processing time for registration adjustment can be shortened.
Further, in the first adjustment mode, registration adjustment is performed with a printed registration mark of black and a registration mark of a color whose photoconductor is located in a position closest to a black photoconductor. Accordingly, the registration adjustment between black and color can be performed easily.
Moreover, the color whose registration marks should be formed is changed over in accordance with the remaining amounts of toners. Accordingly, lopsided consumption of color toner can be suppressed.
A second object of the invention is to provide an image forming apparatus having a black image forming cartridge and an image forming cartridge in which image formers of a plurality of colors are integrated, in which registration adjustment can be performed with suppressed toner consumption and shortened processing time.
In order to attain the second object, a second embodiment of the invention provides an image forming apparatus including: a black image forming cartridge; an image forming cartridge in which image formers of a plurality of colors are integrated; a registration mark former for forming registration marks on an intermediate transfer belt; a registration sensor for reading the registration marks; and a controller for controlling the registration mark former based on the registration marks read by the registration sensor, so as to adjust registration; wherein the controller has an adjustment mode to adjust registration between black and color.
In addition, the controller may have a first adjustment mode in which a registration mark of one of yellow, magenta and cyan and a registration mark of black are formed individually so as to adjust registration between black and color, and a second adjustment mode in which registration marks of all the colors are formed to adjust registration, and the controller may change over between the first adjustment mode and the second adjustment mode so as to adjust registration.
Further, the controller may adjust registration using a registration mark of black and a registration mark of a color whose image former is located in a position closest to the black image forming cartridge in the first adjustment mode.
Moreover, the controller may change over the color whose registration marks should be formed, in accordance with remaining amounts of toners.
According to the second embodiment of the invention, the image forming apparatus having a black image forming cartridge and an image forming cartridge in which image formers of a plurality of colors are integrated, has an adjustment mode for performing registration adjustment between black and color in which misregistration is apt to occur. Accordingly, the consumption of color toners can be suppressed, and the processing time for registration adjustment can be shortened.
In addition, registration adjustment is performed by changing over between the first adjustment mode in which a registration mark of one of yellow, magenta and cyan and a registration mark of black are formed individually so as to adjust registration between black and color, and the second adjustment mode in which registration marks of all the colors are formed to adjust registration. Accordingly, the consumption of color toners can be suppressed, and the processing time for registration adjustment can be shortened.
Further, in the first adjustment mode, registration adjustment is performed with a printed registration mark of black and a registration mark of a color whose image former is located in a position closest to the black image forming cartridge. Accordingly, the registration adjustment between black and color can be performed easily.
Moreover, the color whose registration marks should be formed is changed over in accordance with the remaining amounts of toners. Accordingly, lopsided consumption of color toner can be suppressed.